The CCQC3 Method for Multi-Component Seismic Responses of Non-Classically Damped Irregular Structures

A new method of complex complete quadratic combination with three components (CCQC3) for non-classically damped irregular structures is proposed in this paper, in which both modal displacement-velocity and velocity correlation coefficients are involved along with the modal displacement correlation coefficients in the normal CQC3 formula. Moreover, the effect of the seismic incident angle on the structural response is considered; and formulas for the critical angle and the corresponding critical response are given. The new CCQC3 formula is as concise as that of the CQC3 method and has explicitly physical meaning. If the correlations among modal responses are ignored, the CCQC3 method is reduced to the method of complex square root of the sum of squares with three components (CSRSS3). Analytical examples are presented in the paper to compare the validity between CCQC3 and CSRSS3 methods. Meanwhile, time history analyses of structures subjected to artificial earthquake waves which are synthesized from design spectra are carried out to verify the complex mode superposition method. The results illustrate that the CCQC3 method is more accurate and suitable for seismic response analysis of important structures; however, the CSRSS3 method may be adopted for general structures in order to simplify the calculation.